Remove Functor instance for Values

Undoes 7267c93

This isn't as attractive as it seemed at first glace, because if the
function mapped over Values changes the Haskell types, the postgresql
types may need changing as well.

Perhaps the original omission of Functor on my part was intentional?

Author: lpsmith

src/Database/PostgreSQL/Simple/Types.hs

@@ -271,4 +271,4 @@ newtype Savepoint = Savepoint Query
 --   See <http://www.postgresql.org/docs/9.3/static/sql-values.html> for
 --   more information.
 data Values a = Values [QualifiedIdentifier] [a]
-    deriving (Eq, Ord, Show, Read, Typeable, Functor)
+    deriving (Eq, Ord, Show, Read, Typeable)